Summary: For this study, adenovirus 12 (Ad12), an oncogenic virus and Ad5 and SV40, generally nononcogenic in mice due to their susceptibility to murine anti-tumor immune defenses, are being titrated for tumor induction in three strains mice that have been genetically modified to make then progressively immunodeficient. These animals will be observed for tumor development for 3-6 months and their ability to sustain tumor development by different doses of virus compared. The data available from these experiments should provide quantitative information on the ability of these animal models to detect and thus rule out the presence of various types of oncogenic agents in cell substrates or products within known levels of sensitivity. During the past year, studies have been initiated to estimate the efficiency with which oncogenic viruses induce tumors in three different strains of immunodeficient mice. THe results of these assays are pending. To evaluate the sensitivity of realtime quantitative PCR assays to detect known oncogenic viruses, primers and probes are being developed for the polyomaviruses, JCV, BKV and SV40. These are viruses which are known to contaminate neoplastic tissues from a variety human tumors and organs. Preliminary data has shown that the primers and probes developed thus far are virus specific and are capable of detecting 5-10 copies of viral DNA per 10ul of the reaction mixture. In addition, these reagents produce signals in proportion to the concentration of the viral DNAs over an 8 log range. Thus, these assays promise to be capable of detecting /ruling out the presence of polyomavirus DNA in terms of the concentration per unit volume of cell substrate and thus per dose of vaccine. The usefulness of these assays is being evaluated by detecting and estimating the number of polyomavirus genomes in DNA extracted from polyomavirus transformed cells, as well as cells from other types of tissues.